Earlier in November, Microsoft announced that they will be retiring MSN Messenger in the first quarter of 2013 (except in China), with service for the chat platform to continue in the form of Skype. Earlier today, the Skype app for iPhoneand iPadwas updated to version 4.2, bringing with it support for MSN Messenger. Now you can sign in and merge your existing Microsoft account and chat with your Messenger, Hotmail and Outlook.com contacts. And if you’re new to Skype, the there’s a new option to create an account right from the app.

imo, the all-in-one chat app that has 700,000 daily users and an average of 50 million messages sent per day, has been updated to version 3.3 on iOS. Aside from the support for iPhone 5′s 16:9 screen, imo’s iPhone interface has been completely redesigned to give its users a more streamlined experience. Gone are the bottom taps, which have been replaced by a left/right swipe gestures that reveal both Profile & Settings (ala Facebook) and accounts for the various services you’ve set up.

Make more than your share of long distance calls? Well Skype is currently running a promo that gives its existing users free worldwide calls for a month. Basically, it’s the Unlimited World subscription plan ($13.99) you’ll be getting free for 30 days. With it, you’ll get unlimited calls to landlines and mobiles in 7 countries (US, Canada, Hong Kong, Guam, Puerto Rico, Singapore and Thailand) and landline calling in 34 countries.

There’s now one more reason to use imo instant messenger on the iPhone. With the latest update, the all-in-one chat app can now make voice calls over Wi-Fi, 3G and 4G between imo users. All that’s required is an iDevice running iOS 3.1+ (or Android phone) and some friends who have imo installed. Unlike other popular messaging apps on iOS (Whatsapp, Viber), imo lets you connect with friends from existing IM accounts, including Skype, MSN, Google Chat, Facebook, Yahoo and more. Other features include group messaging, voice IMs, persistent push notifications (1 week after app closed) and searchable chat history. One other cool thing is that you can head over to imo.im on your desktop web browser and do pretty much the same thing. If you haven’t checked out imo yet, it’s completely free well worth the space on your iPhone/iPad.

Perhaps the most popular (and fastest growing) alternative to Skype, Viber now has 90 million users worldwide and just been updated today to v2.2 for iOS. For the uninitiated, Viber lets its users call and text each other all for free – so long as the app has been installed on their mobile device. With the most recent update, Viber brings group messaging, along with time stamps to all messages sent/received to masses (something Whatsapp users have gotten accustomed to). More importantly for its VoIP functionality, a new voice engine has been implemented for improved sound quality.

Twitter for iOS was updated earlier this afternoon and users will undoubtedly welcome the new additions. Twitter’s expanded tweets feature, which you’ve likely experienced already online (and on the mobile site) has made its way onto the iPhone and iPad (this is being rolled out gradually, so it’s possible that tweets don’t expand for you just yet). For those not familiar, users expanding tweets to partner sites (NYT, WSJ, TIME etc) will see content previews, view images and even be able to play videos right then without leaving the page. One example of this is if you tap on that Kickstarter tweet on your iPhone, you’ll be able watch the project video directly from the Tweet details view in the app.

bitly, one of the most popular link shortening services on the web (25 billion links have been saved since 2008) has not only radically redesigned its web interface, but also introduced some new features that aims at better organizing your URLs. Links are now known as “bitmarks” (think of them as bookmarks for anything interesting you come across on the web) and “bundles”, which are essentially folders which you can assign bitmarks to. They can then be made either private or public, and easily shared with friends and family. Coinciding with the changes, the bitly iPhone app was released today, making it more convenient to keep all those saved links close at hand when on-the-go. With the ability to read your bitmarks offline, bitly can now be used as a read it later tool as well, much like Pocket or Instapaper. bitly for the iPhone is a free download and available now on the App Store.

One of the most popular features found in iOS 5 – iMessage – will be coming to a Mac near you, thanks to the upcoming and next major release of Mac Os: Mountain Lion. In fact, the beta version of Messages for Mac was released earlier today, so current Lion users can get a taste of sending messages to other iDevices right from their Macs. Here’s what you can expect from the highly anticipated chat app:

Send unlimited iMessages to any Mac, iPad, iPhone, or iPod touch.*

Start an iMessage conversation on your Mac and continue it on your iPad, iPhone, or iPod touch.

Vonage, one of the largest VOIP providers in the industry, has released Vonage Mobile, an app that intends with go toe-to-toe with Skype. Like Skype, Vonage Mobile lets users talk and text for free with anyone else who has the app installed, and international calling rates are dirt cheap. In fact, Vonage claims that overseas rates are 30% cheaper than Skype (Based on per-minute rates to the top 50 countries called) and 70% less than major mobile carriers. Conveniently, credits are topped up with your iTunes account. Additionally, even if you’re not a current Vonage home/business customer, you can still place calls to any Vonage number at no cost.

Best of all, for a limited time, Vonage Mobile users can now call the US, Canada or Puerto Rico from anywhere in the world for Free (limit of 3,000 minutes/month). This promotion alone is worth downloading the app just to test out the voice quality over Wifi, 3G and 4G data networks. Check out the video below highlighting the benefits of using Vonage Mobile over Skype.